1. Field of the Invention
The present invention relates to a guide rail mechanism for a bonding apparatus.
2. Prior Art
Conventionally, the guide rail mechanisms used in bonding apparatuses such as die bonding apparatuses and wire bonding apparatuses, etc. include, as shown in FIGS. 9 and 10, a pair of guide rail sections 2A and 2B which guide both sides of a workpiece such as a lead frame 1. Since these guide rail sections 2A and 2B have more or less the same structures, the same or corresponding members will be described using the same reference numerals.
A pair of width adjustment guides 4 which extend in the direction of width of a lead frame 1 being conveyed are disposed on the upper surface of a stand 3, and a slider 5 which is moved by a driving means (not shown) is slidably disposed on each of the width adjustment guides 4. Here, the "direction of width" and "inside" of the lead frame 1 are indicated relative to the direction of the position of the heating block 14 (described later) which is located substantially in the central portion of a guide rail stand 8 (also described later) as shown in FIG. 9. A sliding block 6 is provided on the slider 5, and a supporting block 7 is fastened to the sliding block 6; in addition, a guide rail stand 8 is fastened to the inside surface of the supporting block 7.
A screw shaft 9, which extends vertically upward and is provided with an internal thread 9a formed in its upper end part, is fastened to each of the guide rail stands 8. A rail height adjustment spacer 10, which is inserted into the screw shaft 9, and a frame guide rail 11 are provided on the surface of each guide rail stand 8. Furthermore, a spring 12 is mounted on a portion of the screw shaft 9 on each frame guide rail 11, and a bolt 13 is tightened in the internal thread 9a of the screw shaft 9, so that the rail height adjustment spacer 10 and frame guide rail 11 are fastened in place by being pressed against the guide rail stand 8 by the spring 12. Furthermore, a heating block 14 which heats the lead frame 1 is disposed between the frame guide rails 11. This heating block 14 is raised and lowered by a driving means (not shown).
Guide rail mechanisms of this type are described in, for example, Japanese Patent Application Laid-Open (Kokai) Nos. S55-26696 and S60-63935 and Japanese Patent Application Publication (Kokoku) No. 63-56121.
In the above prior art, the lead frame 1 is fed along the guide sections 11a of the frame guide rails 11 to the bonding position by a feeding claw (not shown). Following positioning, bonding is performed by a bonding apparatus (not shown) to the lead frame 1. In a die bonding apparatus, semiconductor pellets are bonded to the surface of the lead frame 1; while in a wire bonding apparatus, wires are connected between leads of the lead frame 1 and pads on the semiconductor pellets are bonded to the surface of the lead frame 1.
Thus, in bonding apparatuses, semiconductor pellets are bonded to the surfaces of lead frames, or wires are connected between the leads of such lead frames and the pads of semiconductor pellets. In this case, the upper surface of the lead frame act as a reference surface at the height position during bonding. Accordingly, if the thickens of the lead frame changes as a result of a change in the type of workpiece (lead frame, for instance) to be handled, e. g., in cases where the workpiece to be handled is thicker than a previous workpiece that has been handled, the height of the upper surface of the lead frame, i. e., the upper surface of the reference surface, is heightened; and as a result, the frame guide rails 11 must be lowered so as to compensate the difference in thickness, thus keeping the height of the reference surface at a constant value.
More specifically, it is necessary to change the rail height adjustment spacers 10 which have a thickness suited to the thickness of the lead frame to be handled. The rail height adjustment spacers 10 are changed as follows: the bolts 13 are loosened and removed from the screw shafts 9, the frame guide rails 11 and rail height adjustment spacers 10 are removed, new rail height adjustment spacers 10 are installed, the rail height adjustment spacers 10 and frame guide rails 11 are put back, and then the bolts 13 are tightened back in the screw shafts 9.
Especially in cases where the guide sections 11a of the frame guide rails 11 are angled C-shaped ("[") rails and angled reverse-C-shaped ("]") rails as shown in FIGS. 9 through 11, it has conventionally been necessary to replace the frame guide rails 11 entirely if the thickness t of the lead frame 1 changes greatly. Ordinarily, the thickness t, as seen in FIG. 11, of a lead frame is in the range of 0.1 to 0.4 mm. Accordingly, the height h of the guide sections 11a of the frame guide rails 11 is obtained by adding a clearance c to the thickness t of the lead frame 1 so that lead frame 1 can be conveyed. Consequently, in cases where the thickness t of the lead frame 1 is within the height h of the guide sections 11a, it is necessary to replace only the rail height adjustment spacers 10, even if the thickness t of the lead frame 1 should vary. However, in cases where the thickness t of the changed lead frame 1 exceeds the height h of the guide sections 11a, the frame guide rails 11 must be replaced with frame guide rails 11 that are suited to the changed lead frame 1.
In the above prior art, in cases where the thickness t of the lead frame 1 changes as a result of a change in the type of workpiece to be handled, it is necessary to loosen and remove the bolts 13, replace the rail height adjustment spacers 10, and then put the bolts 13 back and tighten them. In addition, the pair of frame guide rails 11 are installed so as to extend in the direction in which the lead frame 1 is conveyed; accordingly, each one of the guide rail sections 2A and 2B is provided with two screw shafts 9 along the conveying direction of the lead frame 1, and springs 12 are mounted on the respective screw shafts 9 so that bolts 13 press the frame guide rails 11 and rail height adjustment spacers 10 against the guide rail stands 8 via the spring 12. In other words, each of the guide rails 11 have two screw shafts 9, two screws 12, two bolts 13, etc. As a result, when a lead frame of a different thickness is to be handled, four bolts 13 are loosened and removed, the rails 11 are adjusted for the lead frame to be handled, and then the bolts 13 are remounted and re-tightened. Thus, it requires a long time for adjustment, resulting in a drop in productivity.
Furthermore, a plurality of rail height adjustment spacers 10 with different thicknesses that match the thickness of the changed lead frame must be prepared so as to be used. This creates problems in terms of the control and storage of the spacers 10; moreover, equipment costs are increased. In the case of frame guide rails 11 which have guide sections 11a of the type shown in FIGS. 9 and 10, a plurality of sets of frame guide rails 11 must be prepared. This causes the equipment cost to increase.